The present invention relates to an automatic transmission which may be installed to automotive vehicles.
In general, an oil pressure to connect a multi-plate brake of the automatic transmission installed to automotive vehicles is supplied to an oil-pressure chamber provided behind a piston and controlled by a valve body which is provided at a transmission case. Specifically, the oil pressure is supplied not directly to the oil-pressure chamber from the valve body, but via an oil passage which is formed in a wall portion of the transmission case.
Further, as disclosed in Japanese Patent Laid-Open Publication No. 2007-225020, the transmission case is comprised of a cylindrical body case and an end cover which closes an opening of an end portion of the body case, and in case the multi-plate brake is provided at the end cover, the oil pressure is supplied to the oil-pressure chamber from the valve body via the oil passage formed in the wall portion of the body case and an oil passage which is formed in a wall portion of the end cover.
Meanwhile, in case the multi-plate brake is provided at the above-described end cover and the piston and the oil-pressure chamber are provided at a piston cylinder member (including a cylinder in which the piston slides) which is provided at the end cover, the oil pressure is supplied to the oil-pressure chamber from the valve body via the oil passage formed in the wall portion of the body case, the oil passage formed in the wall portion of the end cover, and an oil passage which is formed in the piston cylinder member.
Herein, in case the oil pressure is supplied to the oil-pressure chamber via the respective oil passages formed in the wall portions of the body case and the end cover, the oil passages may become long and have many bending portions. In case the oil pressure is supplied to the oil passage formed in the piston cylinder member, the oil passages may become longer and have more bending portions. Accordingly, the flow resistance of the oil passages increases and the responsibility of the oil supply decreases, so that the controllability of the multi-plate brake would deteriorate. Further, manufacturing costs for forming the oil passages at the transmission case and the like would increase, and a risk of leakage of the oil pressure would improperly increase due to many connection portions and sealing portions which are formed at the oil passages.